Pressure sensitive record material



Patented Apr. 24, 1951 2,550,473 OFFICE 1.

PRESSURE SENSITIVE RECORD MATERIAL Barrett K. Green and Robert W. Sandberg, Dayton, Ohio, assig'nors to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland No Drawing. Original a pplication July 13, 1948,

Serial No. 38,547. Divided and this application September 15, 1950, Serial No. 185,154

2 Claims.

This invention relates to pressure-sensitive recrd material, and more particularly pertainsto such material having minute particles of two kinds of substances which are color reactive on contact,'one of the substances being in liquid form and the other being in solid form, the particles of the two substances being arranged in proximity in profuse numbers but insulated from contact by material rupturable when pressure is applied, which pressure acts to bring the two kinds of substances together at the points of rupture to produce a distinctively colored localized mark.

This is a division of United States Patent application No. 38,547, filed July 13, 1948, by applicants herein.

The record material of this invention although adapted for response to stylus pressures, is particularly adapted for responseto pressures applied in impact printing operations such as by the striking or pressing of type thereagainst and in that respect is an improvement over the rec ord material of Barrett K. Green's United States Patent 2,505,470, for Pressure Sensitive Record Material, which was granted April 25, 1950.

The record material disclosed therein required the bringing together, by pressure, of two kinds of solid particles embedded in a rupturable solid insulating film. The low mobility of such solid particles rendered that record material more sensitive to pressures caused by drawing a stylus thereover than to pressures derived from the impact of type. This novel record material also is an improvement over that record material disclosed in United States Letters Patent No. 2,299,693, patented on October 20, 1942, on the application of Barrett K. Green. That patent discloses pressure-sensitive record material, especially for impact work, such material including a rupturable insulating medium in which are in terspersed liquid droplets of two kinds which re acton contact to form color. The liquid droplets included solid color-forming materials dissolved in an ionizing medium, glycerine, which reacted to produce color on contact by interchange of ions. Any liquid ionizing medium available for use in such a system is hygroscopic making the record material unduly sensitive to moisture.

The present invention provides a record material with exceptional response toimpact pressures and one having remarkable stability as no ionizing liquid is required. The liquid'used to dissolve the active color ingredient in the liquid reactant substance is anon-ionizing inert oily type of material which is non-hygroscopic and is used solely to dissolve the active ingredient and to ebtain easier release and greater mobility of the droplets when the supporting film is ruptured. Because of the mobility of the released liquid droplets at points of rupture of the insulating medium, the newrecord material is highly sensitive both to drawing and to impact pressures yet it is resistant to destructive influences encountered in ordinary environment and normal handling operations. Thus, the new record material combines the best characteristics of known pressure responsive record materials by providing a novel liquidsolvent reactant structure.

The'principal object of the invention is to providealpressure-sensitive record material on which a mark of distinctive color may be produced by the mere application of localized pressurasaid material including color-forming substances of two kinds, one being solid and the other being liquid, the two substances normally being held insulated from reaction contact by a rupturable insulating 'm'edium until marking pressures rupture the insulating medium at points of pressure to bring about local contact of the two substances to produce a mark.

Another object of the invention is to provide a record material in which one of the color reactant substances is dissolved in a non-ionizing oily liquid which may be dispersed as droplets ma rupturable solidinsulating film so as to be readily available and mobile locally to make contact with theother solid reactant material when re-} leased by rupture of the film.

Another object of the invention is tov provide such a record material" which is highly sensitive to impact pressures such as are met with in typewriter or letter press work and for this efiect the two color reactants are arranged in separate overlying layers on a Web so that marking pressures vertically applied to the said layers will cause penetration of the color reactant substance of one layer into that of the other layer.

Further objects and objects relating to details and economies of production, will definitely appear from the detailed description to follow.

. The objects of thisinvention have been attained by the several embodiments thereof described in detail in the following specification. The invention is clearly defined and pointed out in the appended claims.

. In the preferred form of this invention the liquid droplets of color reactant are dispersed in afilm-forming substance which is applied as a' coating to a paper web and dried thereon leaving the liquiddroplets entrapped therein. The solid color reactant particles, acting as adsorbents, are likewise dispersed in a film-forming substance which is applied as a second overlying coating. Both films are rupturable to force the reactan substances together. Of the reactant materials employed, the liquid droplets contain an organic substance which is an electron donor aromatic compound having a double bond system which is converted to a more highly polarized conjugated form upon taking part:in an electron donor acceptor adsorption chemical; reactiomgiving it adistinctive color; and the-solid particlesare of an inorganic'substance which is an acid relative to the organic substance so as to be an electron acceptor when in adsorption contact therewith, The solidzmaterial is in fine particle formrin orderto :furnishv The adsorbate substance may include-one;or

more kinds of reactant such as crystal violet lactone, which is 3,3 bis ,(pdimethylaminophenyl) fi'edimethylaminophthalide, andtetrachloro malachitegreenlactone mixed together and dissolved in .theoily liquid.

Theweb used as a supportmay be paper or other material suitable as a. recordbase. For instance, either cardboard, glass, metal or wood may be used if desired. The totalthicknessof the pressure-sensitive film. need be no greater than from .001 to .002of an. inch so it may be supported on very thin paper stock. By placing a number of such thin-coated paper sheets in superimposed relation in a typewriter a: number of printed'copies of 'typewritten'material may bev made without the use of a typewriter. ink ribbon or carbon manifold paper as is now. the common practice.

As it isdiflicult, if not*impossible; to: show the exactstructure of this coating by use of a drawing none accompanies this specification;

Inthe followin examples; there" will'bedescribed embodiments ofthisinventionby which the objects of the invention have beensuccessfully attained.

Ea'mmpZeL-The following embodimentof this inventionconstitutes the best mode of applying the principles thereof as contemplated upto the present time'and may be considered the preferred embodiment. It comprises a' base webof paper,

or-the'like, on one surface of which two-coatings are applied, the first or undercoating being" an insulating film in which are entrapped a" profuse number of liquid droplets inwhich a-color react-'- ant substance is dissolved. Thesedroplets are, on" the average, of the order of from l'to microns in diameter and are spaced apart; on-the average, a distance of the order of /2'micron; The preferred thickness of this first coating, when dry, is of the order of .001 of an-inch.

The first coating is made by dissolving one part by weight of animal gelatin, having an isoelectric point of pH 8 and a jelly strength of 275 grams as measured by the-Bloom gel'ometer; with three parts byweight of water heated to' 150 Fahrenheit.

Into four parts by weight of the gelatin solution there is dispersed, or emulsified, three parts byweight of a solution of'crystal violet lactone in chlorinated diphenyl;

This solution of crystalviolet lactone, which is 3,3 bis(p-dimethylaminophenyl) -6'-di'methyl amino phthalide, in'chlorinated' diphenyl is made by dissolving three parts by'weightofthe crystal violet lactone in ninety-seven parts by weight'of chlorinated diphenyl which has a chlorinecontentaveraging 48' per cent by weight. This chlorinated diphenyl solution is heated to the temperaturev of the" gelatin solution before it is addedthereto and emulsified;

The emulsionis applied while still: hot; or? if alldwed:tor coolxafter reheatingtto 150 'F. andsis dried'eitherunder normal. atmospheric conditions or by artificial means such" as a hot air blast or on a heated drying drum such as is commonly used in paper coatin machines. It is considered that drying under normal atmospheric environment" givesasomewhat better water resistance tothe dried film or coating in which the chlorinated. diphenyl solution droplets are entrapped.

The dried .undercoating is next treated to drive the droplets "out of the top surface layer and into theinterior' of :tthe.film so as, in effect, to form an. impermeable surface skin thereon. This is accomplished by wettingthe surface with water at room temperature, that is from 70-80." Fahrenheit, which water has had addedlthereto 1 per. cent by weight of formaldehydeand 0.1 per cent by weight of a wetting agent such as dioctyl' ester of sodium sulfosuccinate. The wetting shouldbe allowed to'persist for. several minutes and thereafter the film is dried in' a low humid: ity atmosphere; The surface wetting may be ac complished by floatingthe coated paper on'the water; coated face'down, or by carryingiton a partially submerged drum with the coated-sur face facing outwardly. The formaldehyde may be omitted; if desired.

The second, or overcoating, then is applied' to the dried undercoating; In making the second coating 20 per cent, by weight, of paper'coating starch in water is co0ked at200" Fahrenheit for 15' minutes and cooled to roomtemperature; Separately, 1 part by weight of finely divided particles of magnesium trisilicate, preferablyof 10 micron size or under, is dispersed in three parts by weight of water by use of 'a' ball mill or equivalent. Four parts, by weight, of the mag-j: nesium trisilicate dispersion is mixed with onepart, by weight, of the starch solution. Theresultant mixture is applied, at room temperature, as an overcoating to the prepared paper having the gelatin coating dried thereon. This starchmagnesium tri'silicate overcoating' is applied in any convenient manner, as by a paper coating machine.- This overcoating' when dry should have a thickness of 'the order of '.0005' of 'an'inch:

The thickness of" the undercoat ing' and the overcoating may be varied somewhat without in terfering greatly with the sensitivity of the material, such variation range beingof the order of 25 per cent'in either direction;

This record material'when finishedhas a sub stantially white appearance and'produces a dark blue mark which sharplydefiiies the area of pres* sure or impact.

The impact of a marking instrument on' the surface of this record material locally releases. the oily droplets from the gelatin'film and forces: them into contact'with the overlying magnesiumtrisilicate particles;

The compound crystal violet lactone has? the structure and i the process. of f makingtit': is described; in:

United States Letters Patent No. 2,417,897, issued March 25, 1947, on the application of Clyde S. Adams filed June 16, 1945, which patent was reissued on August 17, 1948, under No. Re. 23,024.

Example 2.-Another embodiment of the invention is the use of malachite green lactone, that is to say 3,3 bis (p-dimethylaminophenyl) phthalide, having the structure (CHS)2N-O morn o in in place of the crystal violet lactone of Example land in the same amount. This gives a substantially white record material producing a green mark when pressure is applied.

Example 4.-Another embodiment of the invention is the use of 3,3 bis(diethylaminophenyl) G-dimethylamino phthalide, having the structure (C2HB) 2 N 2 0) a w ah in place of the crystal violet lactone of Example 1 and in the same amount. This gives a substantially white record material producing a blue mark when pressure is applied. Magnesium trisilicate seems to be of such structure as has available interior adsorbent surfaces and therefore is particularly suitable to act as the adsorbent material of the system.

The methods and processes of making the pressure-sensitive record material as disclosed herein are disclosed and claimed in a copending application of Barrett K. Green and Robert W. Sandberg, Serial No. 38,548, filed July 13, 1948.

It is understood that the pressure-sensitive record material described herein is susceptible of considerable variations without departing from the spirit of the invention.

What is claimed is:

1. Pressure-sensitive record material including the combination of color-forming substances of two kinds, one kind being solid and the other kind being liquid, said liquid kind being held insulated from contact with the solid kind by being profusely dispersed in minute droplets in a solid rupturable film on the exterior of which is deposited a, film bearing particles of the solid kind, the application of localized pressure to the record material rupturing the film at points of application and there bringing the color-forming substances together, whereby a distinctively colored mark is produced by mere application of localized pressure, the solid color-forming substance being magnesium trisilicate, and said liquid color-forming substance being an organic electron donor aromatic compound having a double bond system which is converted to a more highly polarized conjugated form upon taking part in an electron donor-acceptor adsorption chemical reaction, giving it a distinctive color.

2. Pressure-sensitive record material including the combination of a supporting Web; a continuous rupturable solid insulating film applied thereto said film containing dispersed therethrough a profusion of minute liquid color-forming inclusions; and a coating on the outer surface of the insulating film, said coating containing a profuse number of solid color-forming particles which, when brought into contact with the liquid inclusions by application of localized pressure to the record material which ruptures the insulating film and coating, react with said liquid inclusions to form a distinctively colored mark at. said points of localized pressure, the solid color-forming particles being magnesium trisilicate, and said liquid color-forming substance being an organic electron donor aromatic compound having a double bond system which is converted to a more highly polarized conjugated form upon taking part in an electron donoracceptor adsorption chemical reaction, giving it a distinctive color.

BARRETT K. GREEN. ROBERT W. SANDBERG.

No references cited. 

